3D hydrogel fibers based system to design heterotypic bone vascularization approaches

Angiogenesis, a critical process in bone formation, development, remodeling and healing, relies on the growth of new blood vessels and on the organization of tridimensional vascular networks. This process, sustained by endothelial cells of microvasculature origin, is finely orchestrated by osteoblastic cells. Recently, we have proven that the SSEA-4+ sub-population, selected amongst heterogeneous adipose-derived stem cells (hASCs), is capable of differentiate towards the endothelial and osteogenic lineages [1]. Even though 2D co-cultures provide powerful insights about heterotypic cellular crosstalk, 3D platforms that more closely translate their native microenvironment allowing mimicking their functionalities, have increased relevance. Naturally occurring polysaccharide kappa-carrageenan (κ-CA) hydrogels have been exploited as cell carries. Upon cooling and under appropriate salt conditions, k-Ca undergoes coil-helix conformational transitions forming hydrogels [2]. Herein, we propose an innovative 3D co- culture system based on κ-CA hydrogel microfibers loaded with endothelial derived SSEA-4+hASCs incorporated within a κ-CA hydrogel matrix containing osteo-derived SSEA-4+hASCs, as a bone tissue strategy. Therefore, the κ-CA fibers, carrying the endothelial cells, are expected to act as promoters of vascularization within a 3D system, loaded with osteogenic cells aimed at assisting bone regeneration.